The invention relates to an inverter for a thin flat product, especially for printing substrates in a printing machine with belts positioned over two deflection pulleys that are set at 180xc2x0 between the deflection pulleys.
Inverters are known in particular for handling of printing substrates, for example, in printing machines. The printing substrates are inverted for two-sided printing with such an inverter. However, other applications are also conceivable, for example, in further processing of printed substrates after printing.
An inverter is known from DE 29 07 110 C2. This is an inverter of a folding machine. The problem in such inverters relates to exact transport of the product, in which this is supposed to be positioned as precisely as possible after inversion. This is a requirement essential for printing quality, especially for inverters in printing machines that are set up for verso printing. It is supposed to be avoided that the product loses its alignment. The product must therefore be securely held between the belts and it must be guaranteed that the belts are not moved from their reference position by transverse forces, especially as a result of product transport.
An inverter for x-ray film sheets is known from DE 24 44 697 A1, which is equipped with transport rolls. These ensure that the x-ray film sheets are acted upon with a sufficient holding force by the alternate application of transport rolls. However, the x-ray film sheets lie fully between the transport belts and these are connected to each other in the variant with inversion on one side, since the two transport belts form by center folding of a material web. In this manner transverse forces cannot act on the transport belts so that they can be moved out of their reference position by the transverse forces, especially their mutual relative position. However, the transport belts in a typical inverter cannot be connected together in the manner just mentioned, since the product being transported is taken up at the site of the merging of the moving belts and leaves the inverter again at the site of separation of the belts.
The underlying task of the invention is therefore to configure an inverter so that the product and the belts move precisely in their reference positions.
The task is solved according to the invention in that at least three guide rolls are mounted on the supporting strand side of the belts in alternate arrangement viewed in the transport direction after the setting region and at least one of the guide rolls has a retaining collar on at least one side.
Because of the expedients according to the invention, the product is securely held between the strand side of the belts serving for product transport, in which the at least one retaining collar is mounted on one or more guide rolls, in order to stabilize running and the holding force of the belts also between the deflection pulleys. It is then expedient to mount the retaining collar on the side of the rolls on which transverse forces must be reckoned with, which can laterally deflect one or both belts. In particular, when an inverter must invert heavier flat products with a wide projection above the belts with high speed, at least one such retaining collar is essential. These requirements exist in particular in the inverters of printing machines.
Modifications of the invention serve to optimize the precision of inversion of the product, applying holding forces where these are essential for secure holding of the product and eliminating transverse forces where these occur.
One embodiment of the invention proposes that a retaining collar be situated on the side on which the outer edge of the product moves upward after the setting region. The second upper guide roll after the setting region then expediently has a retaining collar, since the largest transverse force from the oblique position of the product occurs there. Generally it is sufficient if two upper and one lower guide rolls are arranged after the setting region.
In order for the product to be held between the belts with sufficient forces, it is proposed that the guide rolls lie against the belts so that these are deflected from the linear direction.
In addition to the guide rolls following the setting region, it can also be proposed that at least one guide roll be arranged in or before the setting region. In this case a guide roll is expediently arranged beneath the supporting strand side of the belts in order to guarantee clean running of the belts and a certain pressure force for the products. Sagging of the belts as a result of the weight of the product can also be avoided in this manner.
If a product that protrudes over the belts to a greater extent than is normally the case in printed substrates is to be inverted, it is additionally expedient if at least one guide device that guides the product is arranged on at least one outer side. A guide device can thus be arranged to guide the outer edge that moves downward after the setting region. This is particularly expedient in harder, stiffer papers or similar products so that these reliably reach the plane for further transport at the end of the inverter. A guide device can also be provided so that it lifts the outer edge to the inversion zenith. This is particularly expedient in flexible papers so that these can be reliably brought to the outer side at the correct time despite their tendency toward sagging. The last two named guide devices are expediently continuous guide rails, for example, in the form of a stable wire that is bent and arranged according to the motion trend of the product.
For the edge of the product that moves downward in order to then be raised back to the horizontal plane after inversion, it is expedient if a guide device is provided that lifts the upward moving edge toward the end of inversion toward the horizontal plane. In addition, another guide device should be arranged that supports the downward moving edge in the horizontal end toward the end of inversion. This is the edge that passes through the zenith and which is not supposed to move beneath the horizontal plane so that the product can be reliably further transported.
The guide devices can be configured in a variety of ways. For example, both of the last named devices can be correspondingly configured sliding surfaces. However, other embodiments are naturally also conceivable.
A wide variety of belts can be used as belts. Flat belts, are more widely configured flat belts can be involved, or it is possible to provide several parallel running belts. A preferred variant, however, proposes that the belts be designed as V belts, since these exhibit high stability. It is expedient at least for V belts if the deflection pulleys are equipped with retaining collars on both sides at least where they serve as drive pulleys. High force transfer is possible on this account. Both the deflection pulleys and additional rolls can be configured so that the retaining collars are designed freely rotatable relative to the rolls. In this manner the belts can be guided without increased friction occurring in the region of the retaining collars between them and the belts. Wear is kept low because of this.
Since the belts are deformed by setting and V belts in particular exhibit different angular positions of their flanks in different deformation regions because of this deformation, it is expedient if the angles of the holding surfaces of the retaining collars are adjusted to the angular position of the flanks of the belt at the location of the corresponding roll. For example, it could be established that the angle of the flanks of the V belt in the region of the retaining collar of the deflection pulley was 25xc2x0 and the flanks have an angle of 34xc2x0 by setting of the V belts in different regions of the inverter. If this fact is considered in configuring the retaining surfaces of the retaining collars, clean support of the belts on these retaining surfaces occurs and thus clean, precise and wear-free running of the belts.
In addition to the aforementioned rolls, one or more additional path-holding rolls can be arranged for the belts. In order to guide the belts properly, it is then expedient if one or more path-holding rolls have retaining collars on both sides. It can be prescribed that at least one path-holding roll be arranged on the strand side of the belt that guides the product or if one or more path-holding rolls are arranged on the return side of the belt. In the latter case, the at least one path-holding roll can be arranged so that it prevents a collision of the product with the return side of the belt.